Perhaps it's because of the language barrier, but I'm not sure I fully understood the answer.
The reason I'm asking you this question is that a lot of people decide to bring luggage into the cabin because they're afraid it will be lost if it's put in the cargo hold.
If all carriers force consumers to put their luggage in the hold when they're already afraid of losing it, they're ultimately being forced to accept a situation that's the opposite of what they want. Wouldn't you agree?